Grinding device



Oct. 10, 1967 I A, KUDERKQ 3,345,884

GRINDING DEVICE Filed Sept. 18, 1964 INVENTOR RONALD A. KUDERKO v BY v 9;, are/ @Z;

United States Patent 3,345,884 GRINDING DEVICE Ronald A. Kuderko, North Chicago, Ill., assignor to Ammco Tools, Inc., North Chicago, III., a corporation of Illinois Filed Sept. 18, 1964, Ser. No. 397,431

9 Claims. (Cl. 74-574) ABSTRACT OF THE DISCLOSURE Device for dampening vibrations in a brake disk during a grinding operation includes a generally U-shaped, rigid frame member formed of magnetic material surrounding the arbor of the lathe supporting the disk, and a plurality of permanent magnets connected in spacedapart relationship to the frame by a plurality of pole pieces. The permanent magnets magnetically attach the device to the surface of the disk. The device also includes a diamond nib tool supporting holder for dressing the grinding wheel prior to the grinding operation.

The present invention generally relates to grinding devices, and it relates more particularly to a new and improved device for preventing relatively thin parts such as the discs used in brakes and the plates used in clutches from vibrating during grinding or machining of the facial surfaces thereof, and for dressing a grinding wheel used in such operation.

Brake discs and clutch plates have large facial surfaces which are adapted to be frictionally engaged by a cooperating member which is rotatable relative thereto. It is important that the facial surface or surfaces of the 'clutch plates and brake discs be exceedingly smooth and fiat, and this is ordinarily accomplished in a grinding operation wherein a rotating grinding wheel engages and thereby abrades the surface of the disc. The common practice is to mount the clutch plate or brake disc on the arbor of a lathe and to rotate it at a high angular velocity simultaneously with the rotation of the associated grinding wheel. Inasmuch as clutch plates and brake discs are relatively thin in their cross-sectional dimension as 'compared to their relative rad-ii, vibration of the plate or disc, as the case may be, generally occurs thereby making it difiicult if not impossible to grind a true, planar surface thereon.

A principal object of the present invention is, therefore, to provide a new and improved method and apparatus for attenuating or entirely eliminating such during the grinding operation, thus facilitating mounting and removal of the dampening device on and from the workpiece.

In a preferred embodiment of the invention, the dampening device also includes a diamond nib tool supporting holder for dressing the grinding wheel prior to the grinding operation. When so used, the vibration dampening device is initially attached by magnetic attraction to the side of the disc to be ground and the grinding Wheel is then dressed by the diamond nib so that its surface will extend parallel to the face of the workpiece to be ground during the subsequent grinding operation. After the wheel has been dressed, the vibration dampening device is removed from the workpiece and placed on the opposite side thereof so that during the subsequent grinding operation vibration of the workpiece is substantially prevented.

Further objects and advantages and a better understanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawing, wherein: v 1

FIGURE 1 is an isometric view showing the vibration dampening device of the present invention being used to .vibratio n during the grinding or machining of thin memrigid frame member having a relatively extensive planar surface which is held in engagement with the workpiece only by magnetic attraction between the dampening device and the associated workpiece. Relative movement between the workpieceand thedampening device is thus possible. In a preferred embodiment of the present invention, the vibration dampening device comprises a 'U-shaped frame member formed of a magnetic material and having mounted thereon a plurality of spaced apart permanent magnets. The U-shaped frame partially surrounds the arbor of the lathesupporting the workpiece dampen vibrations in a brake disc during a grinding operation;

FIGURE 2 is a side elevational view of the device of FIG. 1;

FIGURE 3 is a plan view of the device of FIG. 2 looking at the left-hand side thereof;

FIGURE 4 is a fragmentary, isometric view of the central portion of the dampening device of FIGURES 1, 2 and 3; and

FIGURE 5 is a fragmentary sectional view of an alternative embodiment of the present invention enabling adjustment in the overall size of the vibration dampening unit.

Referring now to the drawing, and particularly to FIGURE 1 thereof, there is shown a brake disc 10 having a hub portion 11 fixedly secured thereto mounted on the arbor 13 of a lathe (not shown). The manner in which the hub 11 is fixed to the arbor 13 is of no importance to the present invention and any suitable means may be used for this purpose. During a typical grinding operation, the disc 10 is rotated by the lathe and a grinding wheel (not shown) is moved across the rearward face of the disc as shown in FIGURE 1.

The disc 10 is relatively thin and in order to prevent it from vibrating during the grinding operation, there is provided in accordance with'the present'invention a vibration dampening unit 15 which is held against the forward face of the disc 10 by magnetic attraction between the device 15 and the disc 10. It will be appreciated that the device 15 of the present invention is adapted only for usewith discs which are formed of magnetic material. However, since this is normally the case, the device of the present invention finds substantially universal application.

The vibration dampening unit 15 comprises a generally U-shaped frame member 17-formed of a strip of magnetic material and having a rearwardly facing fiat edge surface 19 which lies in a common plane. The frame 17 'is made sufficiently rigid so as to not be deformable under the stresses exerted thereon during use whereby the edge-19 remains planar at all times. For the purpose of facilitating manufacture of the unit 15, the frame 17 comprises a plurality of interconnected straight portions or segments 17a, 17b, 17c, 17d, and 17:2. The portions 17a, 17b, 17d, and 17e are pole pieces for a plurality of associated permanent magnets 18a, 18b, 18d, and 18a. The magnets 18a, 18b, 18d, and 18e are rectangular in shape and may be of any suitable type such as the well known types formed of alnico and magnetizable ceramic material. The magnets each have a permanent polar direction which extends perpendicularly to the adjacent surface of the associated portions 17a, 17b, 17d and 17e of the U-shaped member 17, and they are fixedly secured to the frame 17 by means of a plurality of rectangularly shaped pole pieces 20a, 20b, 20d, and 20a held in place by suitable nonmagnetic rivets 22 extending through aligned apertures in the frame 1-7 and in the pole pieces 20a, 20b, 20d, and 20s. The rivets 22 are sufliciently tight so that the permanent magnets are frictionally held in place between the pole pieces 20a, 20b, 20a, and Ne and the frame member 17.

The pole pieces 20a, 2%, 20d, and 20e each have an edge surface which lies in the same plane as the planar edge 19 of the frame member 17, and the permanent magnets 18a, 18b, 18d, and 18e are spaced inwardly from this plane. Accordingly, each pole piece and the associated segment of the frame member 17 provide the opposite poles of a magnetic assembly and a plurality of magnetic fields are thereby established between each of the pole pieces 20a, 20b, 20d and 20s and the magnetic frame member 17. Accordingly, when the frame member 17 is placed in contact with a surface of magnetic material, the frame member 17 is held by magnetic attraction against such surface.

During a grinding operation when the disc is rotated, any vibration of the disc 10 causes mechanical deformation thereof with a resultant relative movement between the vibration dampening device and the adjacent surface of the disc thereby generating eddy currents in the disc. The energy thus required to generate such currents is absorbed from the energy of vibration thereby attenuating and maintaining the amplitude of vibration in the disc at a negligible level.

Inasmuch as the frame 17 partly surrounds the arbor, any tendency for the unit 15 to slide along the disc 10 is counterbalanced. Also, the irregular spacing of the magnets 18a, 18b, l-Sd and 18a relative to one another also minimizes vibration of the associated disc.

In order to facilitate removal of the unit 15 from the workpiece, a handle in the form of a block 28 is suitably secured to the center section 170 of the frame member by means of a plurality of screws 30 which extend through apertures in the frame 17 and are threadedly received in the block 28. It will be noted that the block 28 has a thickness substantially less than the corresponding width of the frame 17 thereby to provide a finger space between the rearward surface of block 28 as shown in FIGURE 1 and the disc 10. In order to remove the unit 15 from the disc 10, the operator merely places his fingers under the block 28 and pulls the unit 15 away from the disc 10.

At the commencement of a grinding operation, it is frequently necessary to dress the grinding wheel so that its grinding surface is parallel to the surface of the disc being ground. To this end, the block 28 is formed of a non-magnetic material and is provided with an aperture 32 for receiving a generally cylindrical tool holder 33 having a diamond tip dressing surface 34 thereon. The tool holder 33 is held in place by means of a thumb screw 36 extending through suitably aligned apertures in the frame 17 and the block 28 into engagement with the holder 33. The aperture in the block 28 is threaded.

At the beginning of the grinding operation the unit 15 is placed on the side of the disc which is to be resurfaced. The lathe is then operated to rotate the disc 10' and at the same time the grinding wheel is rotated and moved across the diamond dressing nib 34. This is a common operation in the grinding art but heretofore the dressing nib has not been mounted directly on the workpiece by magnetic means. After the grinding wheel has thus been dressed, the unit 15 is removed from the side of the disc to be resurfaced and is placed on the opposite side thereof. The grinding wheel is now moved into engagement with the side of the disc to be resurfaced, and the unit 15 prevents the disc from vibrating during such operation.

Inasmuch as the outer portion of the disc 10 is most susceptible to vibration, the frame 17 should lie in proximity 'to the circumferential portion of the disc 10. In order to enable the same unit 15 to be used most efficiently with different sizes of brake discs and clutches, an adjustable frame may be provided. In accordance with this embodiment of the invention, means for adjusting the overall size of the frame 17 is shown in FIG. 5. As there shown, the central portion of the frame member 17' is provided in two parts and 170" which respectively include a slot 38 and a slot 40. A shoulder screw 44 is threadedly secured to one of the frame member sections 170' and the shoulder portion loosely extends through the slot 40. A bolt 46 is secured to the other member 17c and loosely extends through the slot 38. A wing nut 48 is threaded over the upper end of the screw 46 so that adjustment of the overall size of the dampening unit is readily achieved by loosening the nut 48, adjusting the relative positions of the two frame portions and then re-tightening the wing nut 48.

While the present invention has been described in connection with particular embodiments thereof, it will be understood that those skilled in the art may make many changes and modifications of the illustrated devices without departing from the invention. Therefore, it is intended by the appended claims to cover all changes and modifica tions which fall within the true spirit and scope of this invention.

I claim:

1. Apparatus for use in a machining operation wherein a workpiece is rotated at high speed and is subject to vibration, comprising a rigid frame member formed of ferromagnetic material and having a planar surface for engagement with said workpiece,

pole piece means having a planar surface for engagement with said workpiece,

non-magnetic means fixedly securing said pole piece means to said frame with said planar surfaces being spaced apart and lying in a common plane, whereby relative movement between said pole piece means and said frame is prevented,

and magnetic means operatively connected between said frame and said pole piece for establishing a magnetic field between said frame and said pole piece for magnetically attaching said frame and said pole piece means to said workpiece to attenuate the vibration thereof.

2. Apparatus for use in a surface grinding operation wherein the workpiece is rotated at high speed, comprising a rigid frame member formed of ferromagnetic material and having a planar surface for engagement with said workpiece,

magnetic means disposed in juxtaposition with said frame with one polar surface engaging said frame,

magnetic pole piece means engaging the opposite pole of said magnetic means and having a planar surface, and

means fixedly securing said pole piece means to said frame and to said magnet means with said planar surfaces fixedly secured in a common plane.

3. A vibration dampening device comprising a rigid frame member of generally U-shaped configuration, said member being formed of a magnetic material and having a generally U-shaped planar surface,

a plurality of permanent magnets,

a plurality of magnetic pole pieces each having a planar edge surface, and

means for securing said magnets and said pole pieces to said frame member at spaced apart locations with each said magnet lying between said frame and a respective one of said pole pieces,

said planar surfaces 'on said frame member and on said pole pieces all lying in a common plane.

4. A vibration dampening device as set forth in claim 3 wherein said frame member comprises a plurality of straight sections,

said pole pieces are flat, and

said pole pieces and the associated ones of said magnets are secured to said frame member adjacent to said sections.

5. A vibration dampening device according to claim 4 further comprising a handle member secured to said frame member in spaced apart relationship with said planar surface and providing a finger space for gripping said member to remove said dampening device from a Workpiece.

6. Apparatus for dampening vibrations in a brake disc during a grinding operation wherein said disc is rotated at high speed, comprising a generally U-shaped, rigid frame member formed of ferromagnetic material and having a planar U-shaped edge portion for engagement with one face of said brake disc,

said frame partially surrounding the axis of rotation of said disc,

a plurality of permanent magnets disposed in juxtaposition with said frame and each having a polar direction extending parallel to said -planar edge portion, one pole of each of said magnets engaging said frame,

said magnets being spaced about said axis,

a plurality of magnetic pole pieces each having a straight marginal edge portion,

means securing said pole pieces to said frame and to said magnets with said pieces abutting the poles of said magnets opposite each said one pole, and

said edges of said pole pieces being aligned with said U-shaped edge of said frame.

7. Apparatus for dampening vibrations in a brake disc during a grinding operation wherein said disc is rotated at high speed, comprising a generally U-shaped, rigid frame member formed of ferromagnetic material and having a planar U- shaped surface for engagement with one face of said brage disc,

said frame partially surrounding the axis of rotation of said disc,

a plurality of permanent magnets disposed in juxtaposition with said frame and each having a polar direction extending parallel to said planar edge portion, one pole of each said magnet engaging said frame,

said magnets being irregularly spaced about said axis,

a plurality of magnetic pole pieces each having a flat marginal edge surface,

means securing said pole pieces to said frame and to said magnets with said pole pieces abutting the poles of said magnets opposite each said one pole, and

said edge surface of each said pole piece being coplanar with said U-shaped surface of said frame.

8. A vibration dampening device comprising a frame member formed of a magnetic material and having a planar surface,

a plurality of permanent magnets,

a plurality of magnetic pole pieces each having a planar edge surface, and

means for securing said magnets and said pole pieces to said frame member at spaced apart locations with each said magnet lying between said frame and a respective one of said pole pieces,

said planar surfaces on said frame member and on said pole pieces all lying in a common plane.

9. A device for dampening vibration in a rotatable member formed of magnetic material, comprising a rigid frame member,

at least three magnet means rigidly and fixedly secured to said frame member in spaced-apart and nonaligned relationship,

said magnet means each having at least one planar surface defining a magnetic pole, and

said magnet means being arranged on said frame mem her with said planar surfaces lying in a common plane for simultaneous engagement with said rotatable member,

whereby said deviee may be attached to said rotatable member solely by magnetic attraction between said magnet means and said rotatable member.

References Cited UNITED STATES PATENTS 2,580,839 1/ 1952 Riopelle 74574 2,669,325 2/1954 Raines 188-1 2,690,512 9/ 1954 Geneslay. 2,736,393 2/ 1956 OConnor 1881 2,945,138 7/1960 Strang.

DUANE A. REGER, Primary Examiner. 

9. A DEVICE FOR DAMPENING VIBRATION IN A ROTATABLE MEMBER FORMED OF MAGNETIC MATERIAL, COMPRISING A RIGID FRAME MEMBER, AT LEAST THREE MAGNET MEANS RIGIDLY AND FIXEDLY SECURED TO SAID FRAME MEMBER IN SPACED-APART AND NONALIGNED RELATIONSHIP, SAID MAGNET MEANS EACH HAVING AT LEAST ONE PLANAR SURFACE DEFINING A MAGNETIC POLE, AND SAID MAGNET MEANS BEING ARRANGED ON SAID FRAME MEMBER WITH SAID PLANAR SURFACES LYING IN A COMMON PLANE FOR SIMULTANEOUS ENGAGEMENT WITH SAID ROTATABLE MEMBER, WHEREBY SAID DEVICE MAY BE ATTACHED TO SAID ROTATABLE MEMBER SOLELY BY MAGNETIC ATTRACTION BETWEEN SAID MAGNET MEANS AND SAID ROTATABLE MEMBER. 